"What a Diff'rence a Day Made", also recorded as "What a Difference a Day Makes", is a popular song originally written in Spanish by María Grever, a Mexican songwriter, in 1934 with the title "Cuando vuelva a tu lado" ("When I Return to Your Side") and first recorded by that same year. A popular version in Spanish was later recorded by trio Los Panchos with Eydie Gormé in 1964. The song is also known in English as "What a Diff'rence a Day Makes", as popularized by Dinah Washington in 1959.
